A concrete sideform system is commonly used to manufacture concrete panels and other concrete structures. Sideform systems are suitable for factory casting or site casting of panels.
Factory casting, also known as precasting, of concrete panels usually takes place on a large steel casting bed in a precast yard. The sizes and shapes of the panels are determined by sideforms that are arranged on the casting bed and concrete is poured into the space defined by the sideforms. When the concrete is dry, the sideforms are removed and the panels are lifted from the casting bed for transportation to a site for installation.
On-site or tilt-up casting of concrete panels usually occurs either on concrete slabs or on transportable steel beds. Again sideforms are used to define the size and shape of the panels. Due to space constraints, site casting frequently involves pouring several panels one on top of another. After the lowermost panel is dry it is coated with a release agent, and the sideforms are moved up to define a new panel of the same size or smaller before a second pour. The panels are subsequently lifted into position using a crane. The crane lifts the panels one at a time from the stack and moves them into position.
It is difficult to produce a sharp edge on cast concrete, since concrete is made up of granular particles and the sharpness of the corner is governed by the size of the particles. A sharp edge would also highlight formwork that is not perfectly straight and true and also such an edge would chip very easily. Accordingly, sideforms are commonly shaped to form a 45° chamfer along each edge of the panel.
In order to produce a mould for a panel, the sideforms must be arranged in either end-to-end abutment or transversely (usually perpendicularly) to each other. A combination of these arrangements is required to produce a complete mould. Ends of the sideforms are usually cut square to facilitate end-to-end abutment of sideforms. However, due to irregularities in sideforms and casting beds, gaps are often present between adjoining ends of sideforms arranged in end-to-end abutment.
For sideforms arranged perpendicularly to each other, the chamfer forming profile of a sideform does not match the square end of the abutting sideform and a gap is formed between the two sideforms. The most common method of reducing this gap is to modify the square end of the abutting sideform by cutting and grinding the end to match the chamfer forming profile. Again, irregularities result in gaps between the abutting sideforms.
In both end-to-end abutment and perpendicular abutment of sideforms, the gaps result in bleeding of the concrete mixture through the gaps when the concrete mixture is poured into the mould resulting in flaws in the cast panel.
For a sideform which has been modified, the end must be cut square again to enable the sideform to be arranged in end-to-end abutment with another sideform in subsequent use. Modification of sideforms to enable appropriate abutment gives rise to substantial costs in time, labour and productivity. It also causes wear and tear to plant equipment.